Pumps



March 12, 1963 Filed Sept. 25, 1959 L. H. BROWNE PUMPS 4 Sheets-Sheet 1 IN V EN TOR.

LINDSAY H. BROWNE BY QM, L59,

ATTORNEY March 12, 1963 L. H. BROWNE PUMPS 4 Sheets-Sheet 2 Eiled Sept. 25, 1959 ATTORNEYS March 12, 1963 L. H. BROWNE PUMPS 4 Sheets-Sheet 4 Filed Sept. 25, 1959 Fl G. 4."

INVENTOR. LINDSAY H. BROWNE BY '7' /JM4,4

FIG. 5.

ATTORNE S 3,080,821 PUMPS Lindsay H. Browne, Westport, Conn, assignor to Scott & Williams, Incorporated, Laconia, NE, a corporation of Massachusetts Filed Sept. 25, 1959, Ser. No. 842,260 6 Claims. (Cl. 103-44) The invention relates to pumps, and has particular reference to the pulsating type in which an operating liquid is completely isolated from the liquid being pumped. Pumps of this general type are disclosed in my co-pending application, 697,343, filed November 19, 1957, and in my Patents No. 2,836,121 and No. 2,869,468 dated, respectively, May 27, 1958, and January 20, 1959.

In particular, the invention relates to pumps of large capacity which are used to pump materials such as heavy slurries, sludges, chemicals, or radioactive or sterile products. These pumps operate on a hydraulic exchange principle wherein pressure energy is transferred from a driving medium such as oil to the hydraulic product by means of a pulsator membrane separating the driving medium and product. Pumps of the pulsator type have wide application in industry because of their ability to develop extremely high pressures, notwithstanding the fact that the liquids being pumped may contain corrosive, abrasive, sterile, radioactive or solid materials. As discussed particularly in said Patent No. 2,836,121, a pair of pulsators may be operated so that when supplied with a continuous flow of driving liquid they will provide a substantially continuous flow of the liquid being pumped. That patent also is concerned with minimizing the only deviation from precise continuity of flow, namely the occurrence of short transient pulses, which actually are more in the nature of sound waves than measurable deviations of flow rate.

In said application 697,343, the pulsators are in the form of fairly large and heavy rubber tubes or thimbles. According to that application, as well as the other disclosures mentioned above, the pulsator-s are formed about perforated tubes into which oil, the driving liquid, is pumped under pressure to expand the pulsators, thereby forcing the hydraulic product out of the pumping chamber provided at the outside of the pulsator. Upon cessation of a pulse of hydraulic pressure within the pulsator it relies solely upon its own elasticity to restore it to its collapsed position, and also to return the driving liquid therein to the reservoir. Furthermore, depending upon the operating conditions of the pump, and the head at the pump inlet, the pulsator may be called upon to pull a vacuum in the pumping chamber, thereby placing further reliance upon inherent elasticity of the pulsator to return it to collapsed position. Thus it is apparent that proper operation of the pump is highly dependent upon its pulsator, the failure of which will render the pump totally inoperative.

The pumps described in said prior patent application and patents, and referred to above, have been highly successful in their various applications. However, as

these pumps increase in size toward larger capacities the size, and consequently the cost, of the pulsators increases disproportionately. Since this type of pulsator depends heavily upon its inherent elasticity for proper operationincluding the return of driving liquid to reservoir, collapsing the pulsator, and possibly pulling a vacuum in the pumping chamberit follows that the thickness, strength and weight of a large pulsator must be great. As an illustration, to better visualize and appreciate the problem, such a pulsator might reach eight feet in length and weigh 3-00 pounds or more. It is significant also that in pumps capable of large capacities United States Patent the operating conditions inducing stress and wear on the pulsator may be considerably more severe than in smaller pumps.

The present application is concerned with a new basic design for a large capacity pump which is capable of withstanding severe operating conditions, and wherein the reliance is not upon inherent elasticity to collapse the pulsator. According to the invention, instead of the tubular type pulsator there is utilized an annular pulsator which is collapsed by positive means instead of inherent elasticity, thus reducing the demands on the perfection of pulsator construction required, not only to provide separation of the driving and pumped liquids, but also to meet very demanding elastic properties.

The inner perforated supporting tube has been eliminated and during collapse of the pulsator a quantity of driving liquid is locked within it, leaving a substantially incompressible liquid core under greater than atmospheric pressure. Such a core prevents further collapse of the pulsator by high liquid pressure in the pumping chamber, which pressure may be occasioned particularly by sticking or failure of the discharge valve, or possibly by a positive inlet head.

Furthermore, since a positive pressure is always maintained within the pulsator, leakage of harmful products into the pumping system in the event of rupture of the pulsator will be prevented. In the case of pumping corrosive or abrasive products, as examples, such a feature obviously is desirable.

A further feature of the invention is a stroke limiting device, to be described hereafter, which insures against damage to the pulsator due to over-expansion thereof.

As discussed particularly in said Patent No. 2,836,121, a pair of pulsators may be operated to produce a continuous output by virtue of the fact that the total displacement of the two pulsators remains substantially constant. According to the specific embodiment of the invention disclosed herein the positive means, previously mentioned, for collapsing the pulsator comprises a novel accumulator system, common to both pulsators, which is particularly adapted to this type of continuous flow operation.

Accordingly, it is an object of the invention to provide a pulsator-type pump of large capacity wherein the operation is not highly dependent on the elastic properties of the pulsator, and wherein positive means are provided to restore the pulsator to collapsed position.

A further object of the invention is to provide a pump of large capacity wherein the pulsator is of relatively simple, inexpensive and light construction.

A further object is to provide a pump of the pulsator type wherein, in the event of failure of the pulsator or other operating conditions, leakage of the liquid being pumped into the driving liquid system is prevented.

It is a further object to provide means insuring against damage to the pulsators due to over-expansion.

The foregoing and further advantages of the invention will become apparent from the following description read in conjunction with the accompanying drawings in which:

FIGURE 1 is an elevation of a pump provided in accordance with theinvention;

FIGURE 2 is an elevation of the pump partly in axial I cross-section and partly cut-away;

Referring to FIGURES l and 2, the pumping action of the pulsator 2 is intended to deliver liquid, which may for example be a slurry, from an inlet header 4 to a discharge header 6. For purposes of this description the liquid being pumped will be referred to herein as the product. In its pumping circuit the product, upon collapse of the pulsator 2, will be drawn from inlet header 4 via a one-way check valve 8, T connection 10 and header '12, and through inlet 14 into the pumping chamber 16. Upon expansion of the pulsator 2 the product is displaced and forced under pressure back through header 12 and one-way check valve 7 to the discharge header 6. As will be understood from FIGURE 2, a pair of each of the valves 7 and 8 is provided for the single pulsator 2, and although only one inlet and one discharge valve are sufficient for each pulsator, it is desirable in the hand-ling of products which may contain a large amount of solid materials to provide a pair of such check valves in parallel for each pulsator. This parallel arrangement of the check valves 7 and 8 and the nature thereof are the same as disclosed in my said prior application 697,343. Briefly, however, the check valves 7 and 8 are desirably of the type disclosed and claimed in my co-pending application Serial No. 694,258, filed November 4, 1957. The valve and seat elements are formed of rubber so as to operate consistently and reliably despite the presence of solid material, and are arranged to clear from the valve and seat elements such solid particles as may temporarily tend to accumulate. It will be understood, of course, that other types of valves may be here used, particularly where the product does not present difliculties by reason of abrasive or other solid constituents. The valves 7 permit the flow of product only in the direction of the discharge header 6 and the valves 8 permit the flow of fluid only in the direction from the inlet header 4 to the pumping chamber 16.

The pulsator 2 comprises a flexible, tire-shaped member or casing 18 which is adapted to be expanded by bydraulic pressure introduced through a passage 20 in the pump. Driving liquid is supplied under pressure through a line 22 and passage 20 to expand the pulsator 2, and upon cut-off of driving liquid pressure the pulsator 2 is collapsed by means to be described hereafter. Before proceeding further with the specific description of the pumping elements, it might be well to refer to the particular means disclosed in FIGURE 3 for distributing driving liquid to the pulsator 2. 'Oil has been used as a driving liquid, the main reason being that it concomitantly serves as a lubricant for the pumping elements. 'Iherefo-re, oil will be referred to herein as the driving liquid. It should be understood that here, as in said prior application 697,343, it is contemplated that a pair of pulsators such as 2 are to be provided to work as a pumping unit although, only for purposes of illustration, with the exception of FIGURE only one pulsator 2 has been shown in the present application. For a detailed description of the valve 24 shown in FIGURE 3 reference may be had to said Patent No. 2,836,121. Briefly, however, the valve 24 comprises a valve spindle 2 6 reciprocatory in a ported sleeve 28. Reciprocation of spindle 26' by a pair of members 30 causes the delivery of oil from a pump 32 and supply conduit 34 alternately to a line 22' and the line 22, which line 22 has previously been described as supplying the pulsator 2 illustrated in FIGURE 2. Delivery of oil from pump 32 to lines 22' and 22 is through ball check valves 40 and '42, respectively. When the valve spindle 26 is at the extreme limit of travel in either direction one of the lines 22', 22 will receive oil under pressure, while the other will be vented to an oil supply reservoir by one of a pair of discharge lines 4 4 and 46, provided respectively for lines 22' and 22, which lead to this main oil reservoir.

Pump 32 may be of any of a variety of types, the main consideration being, however, that the pump should be capable of providing an output reasonably continuous and free from pulsation. Desirably, the pump 32 should be adjustable as to delivery rate and for this purpose may, for example, be of the multiple piston type having adjustable displacement. The members 30 for reciprocating spindle 26 are driven by a slide 48, which in turn is reciprocated by a crank 50 and connecting link 52. A motor 54 of suitable type is provided to drive pump 32 as well as to drive, through connection 56, reduction gearing 58, crank shaft 60 and crank 50.

It may be remarked that the rate of rotation of the crank shaft 60 for the purpose of reciprocating spindle 26 through its cycle is such that, considering the maximum delivery of pump 32, if the delivery rate of this pump is adjustable, the pulsators will not be expanded during any cycle to an extent beyond that predetermined to be the desirable maximum. Variation in delivery rate of pump 32 then merely involves less expansion of the pulsators to provide corresponding displacement of the product being pumped.

Summing up the above matter of the distributing valve 24, it will be seen that reciprocation of spindle 26 re sults in a pulsating flow of oil from pump 32 to line 22, which leads to the interior of the pulsator 2, and to line 22, which is intended to supply a second pulsator (see FIGURE 5) operating in conjunction with pulsator 2. The continuous supply of oil from pump 32 involves total displacements of a pair of pulsators (one of which being pulsator 2), first one, then possibly both, and then the other, in such a fashion that the total of the displacements of the two pulsators remains constant. The result is that the flow of pumped liquid is also constant assuming no leakage, which is negligible.

Returning now to describing the specific elements that make up the pump itself, the chamber 16 is defined by a housing comprising the drum 62, which is capped by a heavy platform 64. Mounted atop the platform 64 is an upstanding tubular housing 66 in the form of a heavy T connection. Between an upper plate 70, which may be secured by suitable means such as bolts, and the housing 66 a valve block 68 is provided in liquid-tight engagement with plate 70 and housing 66. Interposed in liquidtight engagement between housing 66 and platform 64 is a spidered bearing 72 that provides lower support for a reciprocating rod 74, the function of which is to effect positive control over collapse of the casing 18. The other end of shaft 74 finds support in a stuffing box 76 mounted in the upper plate 70 and having packing 78 therein.

As previously mentioned, the pulsator 2 comprises a flexible, tire-shaped casing 18. The casing 18 is generally toroidal and substantially C-shaped in cross-section, and may be formed of rubber, preferably of the synthetic type capable of withstanding lubricating oil in its interior and the liquid being pumped on its exterior. Due to the fact that a high pressure differential normally does not exist across the pulsator membrane, the casing 13 need not be made of especially strong material capable of withstanding such pressure differences. The only strength requirement of the casing 18 is that it be able to undergo continuous flexing without rupturing, which would cause leakage, and in this respect also the casing 18 is similar to a tire casing. The upper bead 77 of casing 18 is fixed by being tightly clamped to a protruding ring portion 93 of the platform 64. This clamping is effected by means of a ring 80 secured to portion 93 by bolts 82, thereby pressing bead 77 into a groove or seat 81. The lower head 79 of casing 18 is secured to a dish-shaped member 84 supported at the end of rod 74 by means of a threaded, liquid-tight cap 86. As in the case of upper bead 77, the lower bead 79 is clamped by means of a ring 88, having a seat 89, which is secured to member 84 by suitable meanssuch as bolts 90.

As will be apparent from the description thus far, since the lower bead 79 .of casing 18 is mounted on rod 74,

reciprocation of rod 74 will be tied in with contraction and expansion of casing 18. Thus a flow of oil under pressure, as the driving liquid, through line 22 to the interior of casing 18 will cause expansion thereof, and movement of the rod 74 upwardly (by means described hereafter) will collapse the casing 18. An important feature of the invention resides tin a resilient sealing ring 92, or O-ring, provided in an upstanding rim 91 of member 84. This sealing ring 92 is adapted to abut the portion 93 at the limit of movement in an upward direction to seal off the interior of casing 18 from passage 20 and line 22.

As already emphasized, in the pulsator type pumps disclosed in said application and patents, reliance is placed on the inherent elasticity of the pulsator to return it to collapsed position and return oil therein to a reservoir. However, according to the present invention means are provided to collapse the pulsator 2 by positive action, and such means will now be described. At the top of the pump structure a cylinder 92 is clamped, by suitable means such as bolts, in liquid-tight engagement between an end plate 94 and said plate 70, thereby defining a chamber 100. A piston 96 having a cylinder wall engaging and sealing shoe 98 is fixedly supported at the end of rod 74, and as such is adapted for reciprocatory movement within cylinder '92. A fitting 103 connects a line 104 with port 102 formed in plate 70 and communicating with chamber 100.

Referring now to FIGURE 5, there is illustrated, partly schematically, the accumulator circuit which effects positive return of the pulsator 2 to collapsed position. The accumulator 106 comprises a tank 107, the interior of which communicates by a T fitting 105 with said line 104 and chamber 100. Within tank 107 there are two spaces 108, 110, which are separated by an elastic bag-like membrane 112. This membrane 112, preferably composed of a synthetic rubber resistant to oil, is a sealed envelope that is inflated with air to a pressure such that at the volume deducible from FIGURE 5 the pressure will be high, say in the neighborhood of 400 p.s.i.g. Oil is maintained in the other space 108 at a comparable pressure by an oil pump P. A pressure switch PS responsive to pressure in the accumulator space 108, upon a predetermined drop in such pressure, initiates operation of a motor M for driving the pump P. Thereupon oil is delivered from a reservoir to the accumulator 106 via a check valve V.

At the top of cylinder 92a dome 114 has tapped into its cap 116 a fitting 118 and line 120. The space 121 above piston '96 constitutes an air space which is vented through a common connection 122 to the main oil reservoir.

It will be understood that the single pump shown in FIGURES 1 and 2 is one of a pair of pumps which are adapted to function as a unit, as has been previously mentioned, and it will be noted from FIGURE 5 that a portion of the second pump is shown. This second pump is identical in all respects with the pump disclosed herein in detail, and certain of these identical parts have been identified with corresponding numbers each having added thereto a prime As previously mentioned, the delivery of pump 32 is constant and, due to the action of valve 24, the sum of the displacements of the two pul-sators does not vary. Pistons 96 and 96, being connected directly to the pulsato-rs, displace liquid from cylinders 92 and 92', respectively, in accordance with the displacements of the pulsators and it follows, therefore, that the sum of the displacements of piston and cylinder units 92, 96 and 92', 96' will be fairly constant. An interchange then, of liquid between cylinders 92 and 92 merely takes place, but without an appreciable change in either the pressure or volume of liquid in the accumulator 106. In this manner a constant pressure acting on pistons 96 and 96 is insured to restore their respective accumulator-s to the collapsed position.

The operation of the accumulator 106 as follows:' Beginning with the valve spindle 26 at its left-hand position as viewed in FIGURE 3, spindle 26 starts to move to the right. At this beginning point pulsator 2 may be considered as fully collapsed, While the pulsator (not shown) connected to line 22 is fully expanded. The communication of line 22' with line 34, through ball check valve 40, is gradually cut off, while the port communicating valve 42 with line 34 is gradually cracked open. The spindle also cuts off line 22 from discharge I line 46. Pulsator 2 therefore starts to expand, thereby pulling piston 96 downwardly and displacing liquid from cylinder 92. By the time spindle 26 has moved to the right sufiiciently to completely open line 22 to line 34, however, discharge line 44 will have been cracked open to line 22' and the expansion of pulsator 2 will be accompanied by the collapse of the pulsator connected to piston 96. Piston 96' is, therefore, moved upwardly by the liquid pressure in cylinder 92 and the displacement of liquid from cylinder 92. As spindle 26 finally reaches its far right-hand position in FIGURE 3 line 22 is fully connected, through valve 42, to line 34, and line 22 is completely opened to discharge line 44. Spindle 26 starts to move back to the left and gradually cuts oif line 22 from supply line 34 just as pulsator 2 is reaching its fully expanded position. coincidentally, however, line 22' is cracked open to line 34. For a short instant, it will be noted, both pulsators are connected to pump 32, with one being gradually cut off and the other being cracked open. Pulsator 2 remains expanded until spindle 26 progresses far enough to the left to connect its line 22 to discharge line 46. As this occurs, the pulsator connected to piston 96' is expanding, and the liquid displaced by downward movement thereof flows to cylinder 92. Finally, pulsator 2 is completely collapsed by the pressure of liquid displaced from cylinder 92' and flowing to cylinder 92, and the cycle of operation is complete.

It will be apparent that no matter what the elastic condition of casing 18 may be, there will always be a positive means for returning it to collapsed position. The

accumulator effectively serves as a fluid spring resiliently urging the pulsator into a collapsed condition. When the piston 96 has been propelled upwardly to an extent sufiic-ient to bring sealing ring 92 into engagement with portion 93, the exhaust of oil from within casing 18 will have been completed, and the pulsator 2 will be in its original starting position. The oil trapped by virtue of sealing ring 92 within casing 18 effectively constitutes an incompressible liquid core resisting any exterior effect of the product to collapse casing 18. Furthermore, it is important to note that in the event of a breakdown, leakage of product can go no further than the sealing ring 92, thus preventing the leakage of corrosive materials, abrasives, chemicals or solid materials into the working parts and interior of the pumping system.

The above function of the accumulator 106 should not be considered as entirely negativing the sufficiency of inherent elasticity normally toreturn casing 18 to collapsed position, since obviously its inherent elasticity may have at least some collapsing effect. However, it is unneces sary for the casing 18 to have any inherent elasticity for the reason that accumulator 106 is normally always capable of collapsing the pulsator, unaided by elasticity thereof. The main requirement of the pulsator is that it be capable of expanding and collapsing many times, and in this 1'6. spect it is similar to an ordinary tire casing. Furthermore, as previously noted the pressure is always the same on both the inside and outside of pulsator 2, and therefore it need have no resistance to rupture. The importance of the entrapped liquid core of oil within the pulsator 2 is not to be underestimated, for under circumstances of operation against an extremely high head at the pump outlet, where the line 22 is opened to exhaust at the end of a pumping stroke the high outlet pressure might be sufficient to seriously damage or rupture the casing 18 if valves 7 fail to close. A positive head at the pump inlet also could have the same effect, were it not for the entrapped liquid core.

It should be understood that the casing 18 need not be in a form resembling a tire, although from the foregoing considerations it will be apparent that a conventional tire casing might actually be used. For example, the inside diameter at the lower head 79, corresponding to the diameter of member 84', could be much larger or much smaller, the main consideration being that means are provided to positively effect expansion and contraction of the pulsator 2. For this reason it is apparent that departures from the specific shape of the pulsator 2 could be taken with equal success and without departing from the inventions principles.

If for some reason the accumulator 106 fails to restore the pulsator 2 to collapsed position; or if spindle 26 stops in its right-hand position in FIGURE 3 and does not reverse to move to the left, allowing an uninterrupted surge of oil to the pulsator 2; or if pump 32 delivers an unusually high flow of oil under pressure, it is apparent that the pulsator 2 will tend to expand to an extent possibly beyond its rupturing point. Therefore, there is provided a stroke limiting device. This comprises a sleeve 124 fitted in valve block 68 and having ports 126 communicating with an exhaust port 128. The port 128 may be fitted to any suitable connection for communication with the main oil reservoir. Within sleeve 124 slides a second sleeve 130 which, by means of a coil spring 132 bottomed against a fixed snap ring 134 in the housing 66, is urged upwardly against a snap ring 136 fitted in sleeve 124. It will be seen that sleeve 130 normally covers the ports 126 and, in the absence of a positive force displacing sleeve 130 downwardly, it effectively cuts off the interior of housing 66 and pulsator 2 from any communication with the sump via port 128. Between a pair of snap rings 138, 149 fixed in sleeve 130 there is provided a collar 142 slidably surrounding shaft 74. Downward displacement of sleeve 130 is effected by means of a collar 144 aflixed to rod 74. This collar 144 is so positioned with respect to the length of rod '74 that when a greater than normal volume of oil enters pulsator 2 to extend it beyond a permissible extent, the collar 144- will have traveled downwardly to the point of engaging collar 142, whereupon sleeve 130 is forced downwardly to uncover ports 126. The movement of rod 74 being tied in with expansion of pulsator 2, the pulsator cannot expand beyond a certain point without having sleeve 130 uncover the ports 126 and exhaust the system. When this occurs the pressure within pulsator 2 is relieved to the point of being incapable of further expanding the pulsator.

Another advantage of the present invention perhaps not immediately apparent is that it occupies considerably less space than a pulsator type pump employing tubular pulsators or thimbles. It should be appreciated that pumps having capacities comparable to that for which the presently disclosed pump is intended, say, in the 15,000 gallons per hour range or better, can reach huge proportions. This is a disadvantage in terms of both weight and space. However, the pulsator disclosed herein takes up considerably less floor space than a pulsator of the tubular type having a comparable displacement.

Although the pump has been described as being intended to handle liquids such as slurries, etc., it will be understood that the pump is applicable to the handling of gaseous products, vapors, and the like.

It will be understood that various departures from the specifically disclosed pump may be made without departing from the scope of the invention as defined by the following claims.

What is claimed is:

1. Pumping means comprising an cxpansible member, means producing a pulsating fluid pressure within the member to effect pumping expansions thereof, means defining a chamber at the outside of the member, valve means respectively controlling the flow of a fluid product to and from the chamber, and means for collapsing the member after each pumping expansion comprising: a piston and cylinder unit, an operating liquid system for said unit, :a pressurized gas-filled envelope within the system placing the operating liquid under pressure, and means connecting the unit to said member, said unit acting to urge the member in opposition to said pulsating fluid pressure.

2. Pumping means comprising a pair of distensible diaphragm members, means associated with each of said members and defining first and second chambers at opposite sides thereof, valve means respectively controlling the flow of a fluid product to and from each of the said first chambers, means supplying a driving liquid to said second chambers at a substantially constant and uninterrupted total rate, whereby the total volumetric displacement of said members due to expansions thereof is substantially constant throughout a complete cycle of operation, and means for restoring each of said members to collapsed condition after each such pumping expansion, the last-mentioned means comprising piston and cylinder units each connected to one of said members and operable to collapse the same and a common fluid system for operating said units including a pressurized accumulator.

3. Pumping means comprising a pair of cxpansible diaphragm members, means associated with each of said members and defining a chamber at the exterior thereof, valve means respectively controlling the flow of a fluid product to and from each of said chambers, means producing a fiow of driving liquid to and from the interiors of both said members at a substantially constant and uninterrupted total rate, whereby the total volumetric displacement of said members due to expansion thereof is substantially constant throughout a cycle of operation, and means for restoring each of said members to collapsed condition after each such pumping expansion, the last-mentioned means comprising means operable by fluid pressure to collapse said members, and a common fluid.

system for operating the last-mentioned means including a pressurized accumulator.

4. Pumping means comprising a pair of cxpansible diaphragm members, means associated with each of said members and defining a chamber at the exterior thereof, valve means respectively controlling the How of a fiuid product to and from each of said chambers, means producing a flow of driving liquid to and from the interiors of both said members at a substantially constant and uninterrupted total rate, whereby the total volumetric displacement of said members due to expansion thereof is substantially constant throughout a cycle of operation, and means for restoring each of said members to collapsed condition after each such pumping expansion, the last-mentioned means comprising similar hydraulic piston and cylinder units each operatively connected to one of said members and operable to collapse the same, and a common hydraulic system for operating said units including an accumulator employing a pressurized gasfilled envelope placing the hydraulic system under pressure.

5. Pumping means comprising a plurality of displaceable pumping members, means associated with each of said members and defining first and second chambers at opposite sides thereof, valve means respectively controlling the fiow of a fluid product to and from each of the said first chambers, means producing a flow of driving liquid to and from said second chambers at a substantially constant and uninterrupted total rate, whereby the total volumetric displacement of said members is substantially constant through a complete cycle of opera tion, and means acting on each of said members in a direction to increase the volume of said first chamber and to decrease the volume of said second chamber, the

last-mentioned means comprising piston and cylinder units each connected to one of said members, and a common fluid system for driving said units, said system including a pressurized accumulator.

-6. Pumping means comprising a plurality of displaceable pumping members, means associated with each of said members and defining first and second chambers at opposite sides thereof, valve means respectively controlling the flow of a fluid product to and from each of the said first chambers, means producing a flow of driving liquid to and from said second chambers at a substantially constant and uninterrupted total rate, whereby the total volumetric displacement of said members is substantially constant through a complete cycle of operation, and means acting on each of said members in a direction to increase the volume of said first chamber and to decrease the volume of said second chamber, the laxstunentioned means comprising piston and cylinder units each connected to one of said members, and a common pressurized hydraulic system for driving said units.

References Cited in the file of this patent UNITED STATES PATENTS 250,253 Johnston NOV. 29, 1881 10 Eggleston Aug. 6, Davis Oct. 6, Jensen Nov. 18, Hacker Sept. 19, Adelson Dec. 1, Soberg Nov. 1, Soberg July 31, Veth et a1. Mar. 1, Hughes June 21, Crookston et a1 Jan. 22, Crookston et a1 Nov. 5, Bradley Mar. 25, Browne May 27, Browne Jan. 20,

FOREIGN PATENTS Great Britain Oct. 15, Germany Aug. 19, Australia Jan. 27, 

1. PUMPING MEANS COMPRISING AN EXPANSIBLE MEMBER, MEANS PRODUCING A PULSATING FLUID PRESSURE WITHIN THE MEMBER TO EFFECT PUMPING EXPANSIONS THEREOF, MEANS DEFINING A CHAMBER AT THE OUTSIDE OF THE MEMBER, VALVE MEANS RESPECTIVELY CONTROLLING THE FLOW OF A FLUID PRODUCT TO AND FROM THE CHAMBER, AND MEANS FOR COLLAPSING THE MEMBER AFTER EACH PUMPING EXPANSION COMPRISING; A PISTON AND CYLINDER UNIT, AN OPERATING LIQUID SYSTEM FOR SAID UNIT, A PRESSURIZED GAS-FILLED ENVELOPE WITHIN THE SYSTEM PLACING THE OPERATING LIQUID UNDER PRESSURE, AND MEANS CONNECTING THE UNIT TO SAID MEMBER, SAID UNIT ACTING TO URGE THE MEMBER IN OPPOSITION TO SAID PULSATING FLUID PRESSURE. 